1. Field of the Invention
This invention relates to a semiconductor device, and more particularly to a semiconductor device having a silicon substrate and receiving as input a radio frequency signal.
2. Background Art
Conventionally, semiconductor devices adapted to radio frequency (RF) signals having frequencies above 500 MHz are often based on compound semiconductors such as GaAs (gallium arsenide) or InP (indium phosphide). The reason is that these compound semiconductors have higher electron mobility than silicon, being advantageous to high-speed operation, and that semi-insulating substrates can be easily obtained from these compound semiconductors, allowing reduction of parasitic capacitance.
However, compound semiconductors have a higher material cost than silicon and have difficulty in increasing the wafer diameter. Hence there is a problem of a correspondingly high process cost in manufacturing semiconductor devices from compound semiconductors. On the other hand, recently, semi-insulating substrates having a specific resistance of 1 kQcm or more have been made available also in the form of silicon substrates. Furthermore, a current-gain cutoff frequency of 10 GHz or more has been realized also in semiconductor devices based on silicon substrates. Thus use of silicon substrates is gradually increasing also in semiconductor devices for radio frequency application. With regard to semiconductor devices for radio frequency application, there is disclosed a technique for increasing the operating speed of a semiconductor device by forming a thick insulating film on a silicon substrate and forming circuits and interconnects on the insulating film, thereby reducing parasitic capacitance between the circuits/interconnects and the silicon substrate (see, e.g., C. Tinella, et al., “0.13 μm CMOS SOI SP6T antenna switch for multi-standard handsets”, 2006 Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Dig. pp. 58-61, 2006).
However, a semiconductor device including a radio frequency circuit on a silicon substrate has a problem of the increase of harmonics, particularly second harmonics, of RF signals.